The objectives of this project are to investigate the precise nature of the lipoproteins secreted by rat liver and to determine what changes occur subsequent to hepatic release. The project is also concerned with factors regulating both VLDL and HDL synthesis, such as nutritional states, and to investigate experimentally fatty or nephrotic liver. One major aim is to determine the role of HDL. The methods used will include use of isolated perfused liver and the analytical methods include radioisotopic labeling and separation of the apoproteins.